(1) Giant HnRNA is a high molecular weight pre-messenger RNA synthesized by blowfly (Calliphora) larva epidermis shortly before metamorphosis. So far it has been characterized only in this fly, although indirect evidence points to its occurrence in two other Dipteran larvae. In collaboration with Dr. E. Shaaya giant HnRNA has now been demonstrated in a Lepidopteran species -- the flour moth Ephestia. The pattern of [3H]-uridine incorporation into Ephestia epidermis shortly before pupation is very similar to that in Calliphora. (2) The small protein ubiquitin is a highly conserved "recognition" molecule essential for ATP-dependent intracellular proteolysis. Using a radioimmuno assay, the amount of free ubiquitin has been measured at different stages of the life cycle of the blowfly. Values were highest in the egg and young adult, and lowest in the larva. The ultimate objective of these experiments is to understand the mechanism(s) of the extensive proteolysis that occurs during insect metamorphosis with special reference to the degradation of the major soluble protein of the larva, namely calliphorin.